Off set internal heat exchanger bundles



July 30, 1957 H. E. SHOBE Y 2,301,082

OFF SET INTERNAL HEAT EXCHANGER BUNDLES Filed Jan. 5, 1955 FIG.

1 COOLANT OUT 14 FIG. 2.

i CONDENSER l I 12 i AND t t REFLUX HEAD| 5 3 I3 1 DISTILLATE I c l g 1IS F P r i Z 1 O 5 i 0 P 2 U i COLUMN FEED INVENTOR. H. E.SHOBE BY Zuflwww ATTORNEYS United States Patent OFF SET INTERNAL HEAT EXCHANGERBUNDLES Henry E. Shobe, Bartlesville, Okla, assignor to PhillipsPetroleum Company, a corporation of Delaware Application January 3,1955, Serial No. 479,309

6 Claims. (Cl. 257-198) This invention relates to distillation. In oneof its aspects this invention relates to the arrangement of heatexchangers in a still. In still another aspect this invention relates toan improvement in tube bundle arrangement whereby greater heat transferis obtained.

In the art of distillation or rectification (fractionation), the liquidto be vaporized is passed to a still or still pot where it is heated bysuitable means to a temperature where the liquid is vaporized at theprevailing pressure. The still may be under pressure or vacuum ascompared to the atmosphere. One convem'ent method of vaporizing theliquid is to pass the liquid into a vaporization zone to a predeterminedlevel so as to cover an elongated tube bundle contained in said zone.However, in a given still, for a given distillation, the capacity islimited by the pressure conditions and the temperature of the heatsource circulating in the tubes. If the pressure is fixed and thetemperature of the heat source is fixed, then the capacity can only beincreased by providing more heat transfer surface. This is frequentlyaccomplished by the use of a second tube bundle. Frequently, the twotube bundles are installed in the still side by side but since moststill pots are round, unless the bundle is centered perpendicular to thevertical axis of the still, the bundle will be shortened considerablyand only slightly more heat transfer area is gained by placing the twobundles side by side. In order to obtain the greatest possible length,frequently one tube bundle is placed directly over the'other bundle.This has the distinct disadvantage of vapors passing up from the lowerbundle passing through the upper bundle displacing liquid and therebycutting down liquid-heat exchanger contact.

I have found a novel arrangement of tube bundles whereby maximum heattransfer is obtained when two bundles are placed in a still pot. I alsouse a baffie to improve circulation in the still pot.

An object of this invention is to provide a novel, arrangem ento'f twoelongated heat exchangers in a still' to provide maximum heat transfer.

Another object of this invention is to provide a novel arrangement oftwo tube bundles and a bathe in a still pot to obtain maximum heatexchange surface.

Other objects and advantages will be apparent to those skilled in theart upon reading this disclosure in conjunction with the drawing and theattached claims.

My invention comprises placing two tube bundles horizontally within astill and spaced so that the horizontal axes of the bundles are paralleland in an oblique plane and are on opposite sides of the still verticalcenter plane. A diagonal battle is placed between the two tube bundlesand intersects the plane containing the axes of the two bundles in sucha manner that the upper end of the bathe is on the opposite side of thestill center plane than is the axis of the upper bundle. The horizontaldistance between the axes of the two bundles will be less than thediameter of the bundle so that each bundle will pass through the centerplane of the still.

condenser has a coolant (generally water) inlet 13 and Patented July 30,1957 This arrangement has the advantage of better utilizing the entireheating surface and also provides for accommodating longer tube bundlesthan will the conventional side by side arrangement. The use of thebaffle sets up a circulation which will give good heat transfer.

While distillation columns and still pots can be of any geometric shapethey usually are constructed generally cylindrical. A tube bundleconsists of a plurality of tubes through which the heat source,generally steam, is passed. These tubes are bound in fixed relation oneto the other and the overall shape usually being generally cylindrical.The elongated axis of the still is vertical and the tube bundle ismounted through the side Wall of the column to extend into the still potand usually closely approaching the opposite inner wall or still shell.The tube bundle is disposed so that its elongated axis is horizontal.

This invention can best be described by referring to the attacheddrawings of which:

Figure l is a typical rectification column, partially in section,showing the location of the tube bundles;

Figure 2 is a top view taken along the section 22 of Figure 1 and showsthe off-set position of the two tube bundles, and

Figure 3 shows an end view of the bundles of Figure 2 taken along thesection 33.

Referring to Figure l, a column d is fitted with upper tube bundle 5 andlower tube bundle 6. Each tube bundle is equipped with conduit means 7for admitting steam and conduit means 8 for removing condensate. Thecolumn is vertically disposed and each tube bundle is horizontallydisposed. A bafile 9 is disposed between the two tube bundles to deflectthe vapors rising from the lower bundle away from the upper bundle. Theplacement of the tube bundles will be further described hereinafter inconjunction with Figures 2 and 3. The liquid level It is maintained incolumn 4 above the top of the upper tube bundle 5. In this particularcolumn the feed conduit 13. is located at about the mid-point inthe'vertical dimension of the column or at about the middle plate. Thecolumn is equipped with a condenser and reflux means 12. This a coolantoutlet 14. The column is provided with a means 15 for withdrawingdistillate and a means 16 for withdrawing concentrated pot liquor.

The arrangement of this invention is more clearly shown in Figures 2 and3. The upper tube bundle 5 and the lower tube bundle 6 are showndisposed horizontally in a vertical column 4. A diagonally disposedbafile 9 is shown between the two tube bundles. The line C represents avertical plane drawn along the vertical axis of the column. The line Drepresents a vertical plane drawn along the longitudinal axis of'theupper tube bundle 5. The line B represents a vertical plane drawn alongthe longitudinal axis of the lower tube bundle 6. The line F representsa horizontal plane drawn along the longitudinal axis of the upper tubebundle 5'. The line G represents a horizontal plane drawn along thelongitudinal axis of the lower tube bundle 6.

The horizontal or elongated axis of bundle 5 is disposed parallel to anda distance a to one side of the center plane C while the elongated axisof bundle 6 is disposed parallel to and a distance b to the oppositeside of plane C. The distance a is generally equal to the distance b andthe sum of a+b, shown as w, is less than the diameter D of the tubebundles. The vertical distance H between the elongated axes of the tubebundles is greater than the diameters D'. The bafiie 9 is disposeddiagonally with respect to the center plane C between the two tubebundles. The bafile extends from a horizontal distance on both sides ofthe center plane C at least equal to the distance a below the upper tubeaxis longer than its vertical axis.

' a maximum liquid-element contact.

bundle Sand the distance 1; above the lower tube bundle 6. My inventionhas been described in one of itspre'ferred embodiments. changes whichcan be incorporated without departing from the scope thereof. Forexample, 'the still need not be cylindrical nor would thetube bundlenecessarily be cylindrical. Each tube bundle will have one horizontalThe distances wand 12 are not necessarily the same. The important thingis that the elongated axes of the two'tube bundles be parallel and lieon an oblique plane and each said elongated tube axis be parallel toandlie on opposite sides of a vertical plane passing through theCfifillfif'Of the still. The two bundles can enter the still from thesame .side if desired. vAs has beensa'id, the novel feature of thisinventionis the placing of two elongated heating elementshorizontally'and parallel within the still below the liquid level sothat the elongated horizontal axis of the'two heating elements will lie.on an. oblique plane so that the axes of the two said bundles will beon opposite sides of a ivertical plane passing through the center ofsaid still andparallel to said heating elements. A diagonal baflle isused between the two heating elements, the said baifle so disposed toprevent vertically rising currents or vapor from the lower elementpassing between the tubes of the upper element. a

. Preferably, the two tube bundles will be cylindrical and the verticaldistance between the horizontal .axes of the tube bundles will begreater than the diameters .of the bundles. It will also be the generalpractice to .have the elongated axis of each bundle an equal distancefrom the vertical axis of the still.

Referring now to Figure 3, the liquid surrounding the heating elementscomes into contact with the heat exchange surface and is caused to bevaporized. The vapors from the lower heating element 6 rise and aredeflected V by the baflle 9 so as not to contact the upper heating ele-'ment 5. At the same .time, vapor from heating element rises. All of thevapors rise to thesurface of the liquid and pass upward through thecolumn. By reflecting the vapors in onedirection from the lower element,a circulation is set up in the liquid up and around the-upper element.Such a system has the advantage of incurring In the conventional systemwhere the vertical axes of both heating elements are in the samevertical plane, the vapors from the lower ele-' ment pass upward throughthe upper element displacing liquid and cutting down on the efliciencyof the upper element. a

One advantage of the olf-set arrangement is that the vertical distancebetween the elongated axes of the tube bundles can be less than when onetube bundle is set directly above the other and thereby can be used inapot with a lower liquid level.

Those skilled in the art will see many Those skilled in the art, havingbeen given this disclosure, will see many changes which can be made andvention.

I claim:

1. In a still pot having two horizontally disposed elongated heatingelements positioned below the normal liquid level, the improvementcomprising said heating elements being positioned at diflierentelevationsand being vertically 01f set one from the other and having abattle positioned therebetween to direct fluid currents set up by thelower of said elements from the'upper'of said elements.

2. A still pot comprising in combination a fluid chamber; two elongatedheating elements disposed within said still pot horizontally-andparallel-with their elongated axes lying in a plane oblique withrespectto the horizontal and being on opposite sides of a vertical planepassing through the center of said still .pot and paralleltoqsaidelongated axes; and a bafile disposed between: s aid-elon- V to avertical plane passing through the center of said still 1 pot, theelongated axes Qf'the said two heating elements lying in a plane obliquewith respect to the horizontal and on opposite sides of said verticalplane, the vertical distance between said elongated axes being greaterthan the horizontal distance therebetween; and an oblique bafileintersecting said vertical plane and having a .slope of .oppositedirection than said oblique plane, the .said .baflle extending on bothsides of said vertical plane to intersect V a second and third vertical.plane which areparallel to first said vertical plane and passing through.the center .of the upper and lower elongated heating elements respectively. v p v 5. The still pot of claim 4 wherein the heatingelementsare generally cylindrical.

6. The still pot of claim 5 wherein the heating elements are steambundles.

References Cited in the file of this patent UNITED STATES PATENIS1,844,308 Armacost Feb. 9, 1932' 2,167,333 Foss July'25, 1939 FOREIGNPATENTS 527,817 Great Britain Oct. 16, 1940

